In the summer of 1997, I was a newspaper reporter covering the Centers for Disease Control and Prevention, and I heard from a contact at the CDC that a team was headed to Hong Kong to check out an odd case. A 3-year-old boy had died of flu. That was sad, but not notable enough on its own to send premier disease detectives rocketing around the world. What was extraordinary about the boy’s death was its cause: a strain of flu known as H5N1 that had never been seen in humans before, though it was common in birds and had recently killed 4,500 chickens on a Hong Kong farm. By the end of that year, 17 other Hong Kong residents would become infected, five others would die, and to shut down the epidemic, Hong Kong would slaughter every chicken in the territory, 1.4 million of them.

That worked, for a while. But in 2003, H5N1 appeared again. Since then, it has sickened 607 people around the world, killing more than half of them. It has done something else too. H5N1 and the 2009 H1N1 “swine flu” — a much larger epidemic whose toll of illness and death was recently revised sharply upward — introduced to many people the idea that diseases could jump from animals to humans, and be much more dangerous to their new human hosts than to the animals they came from.

Diseases that jump in that manner are called “zoonoses,” and because their effect can be so dramatic, they are the subject of major international tracking projects, not to mention cultural fascination. (For just one example, watch last year’s movie Contagion.) But a new book, “Zoobiquity: What Animals Can Teach Us About Health and the Science of Healing” (Knopf) argues that by viewing animals only as a source of infection, we miss a rich range of illnesses that we have in common with other species and that could broaden our understanding of what affects our health and theirs.